The Boston Partners Study (BPS) and the Longitudinal HIV Prevention Project (LHIVPP) are two prospective cohort studies of 899 gay and bisexual men enrolled at the Fenway Community Health Center (FCHC) since 1985. The combined FCHC studies represent the largest cohort of prospectively followed high risk and HIV infected persons in New England. In cross-sectional analyses, we have found that when men drank and used drugs before and during anal sex they were less likely to use condoms than when they were sober. This was also observed among HIV discordant pairs who knew their HIV antibody status. The proposed study has the following aims: 1. To explore further the relationship between drinking, drug use and unprotected sex, by evaluating the entire cohort in two waves of data collection six months apart. 2. To compare the HIV status, drinking, drug use and unprotected sex among gay and bisexual couples compared to men not in steady relationships. 3. To evaluate the prevalence of problem drinking and seeking behavior and determine its relationship to alcohol, drug use and unsafe sex. 4. To determine if younger gay and bisexual men (aged 18-24) have different sexual practices, alcohol and drug use than older gay and bisexual men. 5. To determine if bisexual have different sexual practices, alcohol and drug use with their female sexual partners compared to their male sexual partners. We propose to: 1) enroll a cohort of young gay men, 2) enroll a cohort of female partners of bisexual men and, 3) re-interview all currently enrolled gay and bisexual men to obtain information about their drinking and drug use and how it effects their sexual behavior. These relationships will be evaluated in the context of sexual couples and their health beliefs to understand their roles play in high risk behaviors.